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E\'AMSDAL£ LIBRW WEST VIRGINIA RSilY ^IVC ■ttvtrv^uv tt9m^» ■ n o » »* Restricted Circulation Only Bulletin 195 June, 1925 Agricultural lExperiment Station CollriK nf Ayrirulturr, lilrst 13irc(inia Uniurrsttu HENRY G. KNIGHT, Director Morgantown The Standard Deviation in the Weight of White Leghorn Eggs (Technical) BY HORACE ATWOOD Publications of this Station will be mailed free to any citizen of West Virginia upon written application. Address Director of the West Virginia Agricultural Experiment Station, MorgantOwn^i W. Va. AGRICULTURAL EXPERIMENT STATION STAFF FRANK B. TROTTER, A. M., LL. D - President of the University GEORGE R. LYMAN, Ph. D Dean of the College of Agriculture HENRY G. KNIGHT, Ph. D Director of the Experiment Station WALTER "C. SCHNOPP, B. S. Agr Agricultural Editor JOHN C. JOHNSTON Chief Clerk AGRONOMY R. J. Garber, Ph. D. Agronomist T. E. Odland, M. S. Associate Agronomist T. C. Mcllvaine, Ph. D.J Assistant Agronomist K. S. Quisenberry, B. S.*** Junior Agronomist ANIMAL HUSBANDRY E. A. Livesay, M. S.*** Animal Husbandman Chas. V. Wilson, M. S. Assistant Animal Husbandman E. C. Stillwell, M. S. Assistant Animal Husbandman S. S. Wheeler, M. S. Junior Animal Husbandman R. H. Tuckwiller, B. S. Agr.* Assistant Animal Husbandman CHEMISTRY Henry G. Knight, Ph. D. Chemist Chas. E. Weakley, Jr., B. A., Assistant Chemist T. B. Leith, B. A.** Assistant Chemist T. J. Cochran, B. S. Junior Chemist DAIRY HUSBANDRY Ernest L. Anthony, M. S. Agr. Dairy Husbandman H. 0. Henderson, M. S. Agr.*** Associate Dairy Husbandman Warren Gifford, B. S. Agr. Junior Dairy Husbandman G. M. Trout, M. S. Assistant in Dairy Husbandry ENTOMOLOGY L. M. Peairs, M. S. Entomologist W. E. Rumsey, B. S.** Assistant Entomologist FARM ECONOMICS A. J. Dadisman, Ph. D. Farm Economist Paul A. Eke, Ph. D. Junior Farm Economist F. D. Cornell, M. S. Junior Farm Mechanician W. W. Armentrout, B. S. Junior Farm Economist HORTICULTURE M. J. Dorsey, Ph. D. Horticulturist H. L. Crane, M. S. Agr. Associate Horticulturist H. E. Knowlton, Ph. D. Associate Horticulturist K. C. Westover, M. S. Agr.*** Assistant Horticulturist Ernest Angelo, B. S. Agr. Junior Horticulturist L. F. Sutton, B. S. Agr.f Assistant Horticulturist Troy M. Currence, B. S. Agr. Assistant in Horticulture Lewis G. Stark, B. S. Agr. Assistant in Horticulture PLANT PATHOLOGY N. J. Giddings, Ph. D. Plant Pathologist Anthony Berg, B. S. Assistant Plant Pathologist L. H. Leonian, Ph. D. Assistant Plant Pathologist E. C. Sherwood, M. S. Assistant Plant Pathologist POULTRY HUSBANDRY Horace Atwood, M. S. Agr. Poultry Husbandman SOILS E. P. Deatrick, Ph. D. Associate Soil Technologist •In co-operation with the U. S. Department of Agriculture, Washington, D. C. **In co-operation with the State Department of Agriculture, Chareston, W. Va. ***0n leave of absence. tin charge of the Reymann Memorial Farms, Wardensville, W. Va. tin charge of the Maggie Sub-Station, Maggie, W. Va. THE STANDARD DEVIATION IN THE WEIQHT OF WHITE LEQHORISI EQGS The eggs laid by a hen vary in weight. Some of them are considerably heavier or lighter and some only slightly heavier, or lighter, than the mean or agerage weight. Table II shows the weight of the eggs laid by hen No. 315 during each month of her second laying year. The column to the left indicates the weights of the eggs, and the tally marks in the columns headed by the names of the months indicate the number of eggs laic during each month, arranged according to their weight. Fo.' example, in March this hen laid 3 eggs falling in the 53.5 gram class; 2 eggs in the 54.5 gram class, and so on. The heavy hori- zontal line is used to indicate approximately the mean eg<r^ weight for the year which lies between 56.5 and 57.5 grams. From this line of mean weight the eggs are dispersed or scat- tered more or less widely. TABLE I. — Calculating the Standard Deviation of the Weigh": of Eggs Laid by Hen 315 as Shown by Table II. Weight of Eggs in Grains Number of Eggs Product of Num- ber of Eggs Mul- tiplied by ! Weight Sq We by uare of the ght Multiplied the Number of Eggs 50.5 1 50.5 2550. 51.5 1 51.5 2652. 52.5 3 157.5 8268. 53.5 13 695.5 37209. 54.5 21 1144.5 62375. 55.5 27 1498.5 83167. 56.5 31 1751.5 98959. 57.5 30 j 1725.0 99187. 58.5 27 1579.5 92400. 59.5 25 1487.5 88506. 60.5 8 1 484.0 29282. 61.5 6 369.0 22693. 62.5 4 250.0 15625. Total 197 1 11244.5 642873. 11244.5-^197 = 57.079, the mean weight of the eggs for the year. The square of 57 .079 m ultipHed by 197 equals 641827. 642873 — 64182'7 = 1 046. 1046-^197 = 5.309 V .1.309 = 2.30, the standard deviation sought. W. VA. AGR'L EXPERIMENT STATION (Bulletin 11*5 TABLE II. — Frequency Chart Showing Distribution of Eggs Dur- ing the Year, Dec. 1921-Nov. 1922, Laid by Bird 315, Deviation in Weight of Eggs, Mean Weight, and Stand- ard Deviation. 2 9,? ' Dcc(i9ai) J>in(i«2] Feb MCN rtPB M«Y JoriE July flue 5c<n- Oct (Mov too 5 30S 3 / S 3as 33S 35 3 365 37 S 3S5 33. -i f05 1 / S 44fi ■^56 463 483 4 9.5 505 5 /5 52S 1 lit II / / IH1 1 II itni III / / III nil 1 II 1 / / 1 3 13 Zl 555 5 rt.«; 1 III U41 II III Ltn IMIII II 1411 1 II III III 1 1 1 mil II III / 2.7 ,1/ S 73 585 5 9n 1 II III /III .III IM1 III III II III II nil nil / Ml nil (Mil II 1 III unii III II // / / 27 2 5 6 OS 6 13 6 Z5 6 15 6 1 .'i 1 / / II 1 III / III 1 III 1 a 6 4 6 55 66 5 6 75 6SS 695 Bird Nn 3 IK 7o5 r / 5 7 Z5 735 74 5 ^Et&tfT or ■,„p /Jew 179 6m, Z.3 o«A .. 75 5 76 5 77S 78 5 OF Esos 3 Zl 2J 21 Z4 Z4 Z5 25 IS IZ IS 7 Table III shows the weights of the eggs laid by hen No. 355 during her second laying season. By comparing Tables II and III it becomes evident that the Q^g weights are more widely scattered in the latter instance. Standard Deviation The extent of the scattering or dispersion is measured byi the standard deviation which takes into consideration the; amount of departure of each variate, (by "variate" is meant one of the individuals measured or weighed) as based on the meanj or the arithmetical average of all of them. In this publication the standard deviations have been calculated by means of the June. 1925) DEVIATION IN WEIGHT OF EGGS TABLE III. — Frequency Chart Showing Distribution of Eggs During the Year, Dec. 1921-Nov. 1922, Laid by Bird 355, Deviation in Weight of Eggs, Mean Weight, and Stand- ard Deviation. WC<«MT QKArnt OtcfiSiil Jiin/lSm, Fna MCH Apr. n^r T»Ni Jiu-Y /w«. *5£P^ Oct .tto<^ ra-! iO£ 316 32£ JA5 J^/i J35 J&5 OW 306 Y^.^ -Hli 4U ■fZS 43J .arf/i 455 466 <»75 '(&6 4a -! soj S/5 1 II J 52 5 1 1 1 1 f SI 5 1 II J 04J> II 1 nil 1 III! 1 1 M 555 II 1 utt 1 9 as II 1 uu Ufl III III II Zl 57i II nil 1 II /I 1 II nil 1 IS Sfl.-i 1 III III uti II III II III 1 1 P4 .S.9.S II nil III II III II IMI // 23 60s 1 III II 1 1 III III II / n 6'S 1 1 1 II 1 III II II II IS 6ZS II 1 / 1 1 1 II a 655 1 1 1 / 1 s 64.'i 1 1 1 1 Ml 9 655 1 1 z 665 6 75 I 1 J 6as 635 5S IPS ftai^ VciiHT Of £003 sa. ree ev/tn 1 1 lis SrnnoA \io PEvtm /<=/» /^ w ««t3 26 GRnntc. 135 745 755 755 77^ 785 Nur,«,^ OF £o« ■4 -? la 21 20 Zl Zl 16 19 zo IS 179 following simple formula:* Standard deviation =^ - in which "2m-" repre- :m- — na- n sents the sum of the squares of the independent measures or variates, "n" the number of measures or variates and "a" their arithmetical average or mean value. For the purpose of illustrating the method of calculating the standard deviation in the weight of eggs the record of hen 315 is taken and the calculation presented in Table I, page 3, in full. In the same way the standard deviation for hen 355 (Table III) has been found to be 3.26. The two values 2.30 and 3.26 en- ables one to compare the relative variability in the weight of the *Phillips, Monthly Woathej Review, March, 192*2, p. 36. fi W. VA. AGR'L EXPERIMENT STATION (Bulletin 195 eggs laid by hens 315 and 355, and as it is desirable to secure eggs that are uniform in weight this information may be of im- portance in connection with the selection of females when breeding for eggs of more uniform size. The smaller the standard deviation the more closely do the eggs cluster about the mean weight, or in other words, the more uniform they are, taken as a whole. Fowls Employed The fowls employed in this work were standard bred Single Comb White Leghorns. Prior to the beginning of this experi- ment this strain of fowls had not been trapped or bred for egg- production. The fowls were in six flocks designated as A, B,, C, D, E, and F. Each female in A had one or more full sisters in flock B and vice versa. Likewise C and D were sisters and E and F were sisters. Flocks A, C, and E were well fed while young while flocks, B, D, and F were fed rations low in protein and ash constituents so that the increase in live weight was slow. After laying began all six flocks were fed uniformly on a well balanced laying ration. The data used in this discussion cover three years' of pro- duction for A and B, two years' for C and D, and one year's pro- duction for E and F. The laying year in all cases began Decem- ber 1 and ended November 30. All eggs were weighed the day following that on which they were laid, and in this discus- sion double yolked eggs and those abnormally small were disre- garded. Most of the eggs were weighed on a chainomatic bal- ance, and the weights were recorded to one one-hundredth of a gram. Standard Deviation as Influenced by the Age of the Fowl Tables IV to IX, inclusive, give the standard deviations in the weight of the eggs laid by the various females in each flock. The deviation varied from a maximum of 6.14±.24 in the case of bird 327 the first year to a minimum of 1.75±.08 in the case of bird 324 during the third year (See Table IV.) There was no significant difference between the means for the second and third years, but the mean standard deviation for the first year was greater than during the later years. To illus- trate the reason for this greater deviation during the pullet year. Table V is presented showing a typical pullet record. June, 1!)25) DEVIATION IN WEIGHT OF EGGS 7 TABLE IV. — Flock A (Well Fed While Young). Band No. of Bird First Year Standard Deviation Second Year Unweighed Mean 3.53±.13* 2.61±.08 Third Year 801 1 3.61±.14 2.74±.10 2.23±.09; 302 1 3.58±.12 1.96±.07 2.38±.08 308 1 2.06±.13 2.22±.08 2.23±.10 309 i 4.31:t.l5 2.35±.10 3.22±.14 311 1 3.84 ±.14 1.99±.'07 2.16±.09 313 1 3.47±.13 3.26±.12 1.78±.09 315 1 4.65±.17 2.30±.08 3.33±.13 320 1 2.74±.12 2.56±.12 3.43±.18 322 2.80±.10 2.41±.09 2.32±.09 324 2.67±.10 2.25±.09. 1.75±.08 325 3.24±.12 2.49±.10 2.39±.10 326 3.30±.14 4.25±.17 3.02±.12 327 6.14±.24 3.28±.12 2.57±.09 330 3.19±.17 2.24±:.09 2.96±.12 331 2.82±.10 1.72±.08 2.12±.09 332 ' 5.11±.18 2.71±.ll 2.35±.09 333 2.96±.12 3.18±.15 2.86±.13 336 1 2.86±.12 1.99+.08 3.66±.15 342 1 2.57±.09 2.53±.09 3.04±.12 347 1 4.12±.17 2.82±.12 2.58±.1C) 351 i 3.17±.14 3.12±.ll 3.60±.14 355 1 3.43±.13 3.26±.12 4.02±.15 356 1 4.63+.18 2.47±.09 2.46±j09 2.72±.05 ♦The probable error of the unweighed means in this and following tables has been calculated from the formula: -6745 ■ S D. considering each standard deviation as a variate. /n By comparing Tables II, III, and V one may see that the dis- tribution of egg weight is quite different during the first year of production or pullet year as compared with that of later years. With pullets the first eggs laid are small and there is a gradual and fairly regular increase in weight to the close of the year, but with mature hens the eggs laid in winter and spring- are relatively large, with a gradual decrease to the minimum weight in summer and then an increase toward fall. This con- dition tends to throw the distribution closer to the mean in the case of the mature fowls. Table VI shows the standard deviations of the weights of the eggs laid by flock B during the three years of the test. The results as shown in Table VI agree with the results shown in Table IV in that the mean standard deviation for the W. VA. AGR'L EXPERIMENT STATION (Bulletin 195 TABLE V. — Frequency Chart Showing Distribution of Eggs During the Year, Dec. 1920-Nov. 1921, Laid by Bird 305, Deviation in Weight of Eggs, Mean Weight, and Stand- ard Deviation. 29 S OtcOOic jAn(/9i/J F£B ricH Apk May Ju/^E July Aug. 5e(»T. Oct. Nov. or €0^3 30S 3/. 3 SZ.€ .T4 5 35.5 J (5.5 SIS S&S 30.3 4XS ■14 5 1 1 III 1 II II II 1 1 1 3 4 4- •15.5 A6.5 47.5 1 1 1 IHI miiii II nil III mi UtI/ll II III imm mi III II un UtII Mil 1 / IZ IB 30 49. S 1 1 Ufl nil III II 16 50.5 51.5 SZ5 5i5 545 II imi 1 '1 III 1 III nil II nil 1 Ufl III III II III Ill II 1 nil 21 "^ i 9 1 S i 8 SS.S 56.5 5 75 583 S9.X 1 1 / z 1 1 60S ai.6 IJJ5 64S 1 ess 66S 075 (585 59.1 fiian Va. JOS 705^ 7/5 T?5 7J.5 74^ We.ionT c • Eeoa 1 B.9SO O* '97 GH'ir, 735 765 775 745 OF Csas 9 Z4 25 2T if 20 IB Zti u /ao first year was greater than that of succeeding years. There was no significant difference in the fhean deviations for the second year and the third year, and there was no significant difference in the means for flock A as compared with flock B, showing that the poor ration fed the chickens in flock B had no measur- able effect upon the standard deviation in the e.g^ weight. Tables VII and VIII show the standard deviation in the weight of the eggs laid by pens C and D. June, 1925) DEVIATION IN WEIGHT OF EGGS TABLE VI.— Flock B (Poorly Fed While Young), "'■ ' ■" Stan< Jard Deviation " Band No. 1 of Bird First Second 1 Third Year Year ! Year 803 3.17±.16 3.82±.15 1 3.24±.14 304 2.75±.12 2.44±.09 ' 2.51±.12 305 2.97±.ll 2.37it.l0 2. 37+. 10 306 5.49±.19 3.18 + .12 3.78±.20 312 2.74±.14 3.75±.19 3.45±.18 314 3.52±.14 1.71±.07 1.76±.08 316 1 4.39±.18 2.60±.09 3.10±.12 319 4.27±.16 2.34±.09 1 2.70±.ll 323 3.98±.14 2.68±.10 2. 69+. 11 329 ! 2.30±.ll 2.49±.10 3.35 + .14 334 2.35±.10 2.67±.ll 2.44 + .09 335 2.69±.12 2.65±.10 2.83 + .11 337 1 5.57±.27 ! 2.97±.12 2.79 + .11 338 1 2.32±.ll 1 2.38±.10 2.37 + .09 340 2.89±.16 1 3.22±.12 2.90+.11 341 3.75±.17 1 2.92±.10 2.74+.10 345 3.03±.13 ! 2.27±.08 2.14+.08 348 3.18+.17 1 2.40 + .10 2.32 + .13 350 3.54+.20 1 2.54±.ll 2.89+.11 252 3.15±.13 2.64±.10 2.05+.09 354 1 2.66±.ll 2.55±.10 2.87+.12 Un weighed | Mean | 3.36±.13 2.69±.07 2.72+.07 TABLE VII . Flock C (Well Fed Whil e Young). Standard Deviation Band No. of Bird First Second Year Year 401 4.28±.17 2.58+.10 402 3.90 + .15 3.01+.11 40:;; 4.02±.17 2.82 + .11 404 3.48±.16 2.73 + .11 406 3.26±.15 1 2.31+.09 407 3.69±.16 i 2.40+.09 409 5.57±.21 1 3.11+.13 411 4.54+. 21 2.47+.10 415 2.96+.12 2.46+.10 419 2.59±.10 1 2.75+.11 420 3.24±.12 2.45+.11 421 2.42±.09 1 1.81+.07 422 3.28±.17 1 2.68 + .14 424 4.87±.16 1 2.57±.09 428 2.84±.12 1 3.14+.11 431 3.39±.14 I 2.30+.09 432 3.04±.12 1 3.39+.13 434 2.56±.10 2.54+.11 435 3.97±.13 2.38+.08 Un weighed 1 Mean 3.57±.13 1 2.62+.05 10 W. VA. AGR'L EXPERIMENT STATION (Bulletin 195 TABLE VIII.— Flock D (Poorly Fed While Young). Standard Deviation Band No. of Bird First Year Year Second 405 3.84±.19 3.43±:.14 408 4.31+.18 3.74+.16 410 3.39±.14 3.46±.14 413 4.31±.20 2.09±.ll 416 2.54±.ll 2.23±.08 418 2.72±.ll 2.16±.08 423 3.75±.16 2.40±.10 425 3.53±.13 3.52±.16 426 3.17±.14 2.43±.09 427 2.99±.ll 2.37±.09 429 2.07±.ll 2.45±.10 436 3.15±.12 3.15±.10 437 4.54±.19 3.00±.13 438 3.23±.13 2.24±.14 439 2.90±.10 2.26±.09 440 3.27±.15 3.40±.15 441 3.12±.14 2.48±.09 442 1 3.36±.15 3.11±.12 443 4.55±.28 3.06±.12 Un weighed 1 1 Mean 3.41+.10 1 2.73±.12 Comparing the unweighed means for flocks C and D for the first and second years respectively it is seen that there is no sig- nificant difference due to the rations fed prior to maturity. The results with C and D agree with the results derived from flocks A and B in that the standard deviations for the first year were greater than for the second. Table IX gives the standard deviation in the weight of the eggs laid byf flocks E and F. Table IX shows that the unweighed mean standard devia- tion for Flock E was slightly greater than for Flock F, and in this connection it is interesting to bring together the means for the six flocks. This has been done in Table X. June, 1925) DEVIATION IN WEIGHT OF EGGS 11 TABLE IX. — Standard Deviation in the Weight of Eggs Laid by Flock E (Well Fed While Young), and Flock F (Poorly Fed While Young). Flock E Flock F Band No. First Band No. First of Bird Year of Bird Year 500 2.62±.10 530 2.71±.09 501 2.86±.12 551 2.95±.12 502 2.75+.11 1 552 2.75 + .10 503 3.29±.14 553 2.83±.ll 504 3.03±.H 554 1.52it.09 506 3.64±.13 555 3.64±.14 507 2.78±.10 557 2.69±.12 508 2.98±.14 558 2.48±.09 510 3.07±.13 559 3.47±.12 511 2.63+.10 560 3.19±.13 512 3.32+.16 561 2.14±.08 513 2.87±.ll 562 2.04 + .09 514 3.52 + .12 563 2.93±.ll 515 2.69±.10 1 565 2.79±.10 516 1.89±.08 566 3.05±.12 517 3.26±.12 567 4.31±.25 518 2.63±.ll 568 2.60ih.09 519 2.28 + .08 569 2.84±.ll 520 3.83±.10 570 1.82±.07 521 2.50±.09 571 2.04±.08 522 1.87±.07 572 2.33±.10 523 3.50±.13 573 3.79±.18 524 3.28+.12 ! 574 2.31±.ll 525 2.17±.10 575 2.35±.09 526 2.97±.ll 576 2.42±.ll 527 3.50±.12 577 3.24±.13 528 2.54±.10 578 3.30±.13 529 3.23±.ll j 579 3.38±.13 550 3.90±.14 580 2.36±.10 532 3.72±.15 581 2.56±.10 533 2.97±.13 582 3.18±.17 534 3.19±.12 584 2.54+.10 535 3.28±.12 585 2.90±.12 536 2.58 + .09 586 3.14±.ll 537 2.87±.ll 587 3.04±.12 538 4.06±.15 588 3.04±.13 539 3.70±.15 589 2.64±.10 540 4.23±.16 590 2.94±.12 541 2.10±:.08 591 2.86±.ll 542 3.35±.13 592 3.21±.14 543 2.81±.10 593 2.41±.ll 544 4.20±.19 ! 594 2.27±.08 545 2.61±.10 595 2.36±.10 546 1.95±.07 596 2.83±.12 547 3.54±.14 597 3.11±.ll 548 2.91±.ll 598 2.91±.13 549 2.36±.09 599 3.03±.20 600 3.08±.23 Unweighed 1 Mean 3.00±.06 1 2.80±.05 12 VV. VA. AGR'L EXPERIMENT STATION (Bulletin 195 TABLE X. — Comparison of Means for the Six Flocks. Flock Standard Deviation First Year Second Year Third Year A B Difference 3.53±.13 3.36+.13 + .17±.18 2.61±.08 2.69±.07 — .08±.10 2.72±.05 2.72±.07 .00±.08 C D Difference 3.57±.13 3.41±.10 + .16±.16 2.62=t:.05 2.73±:.12 — .11±.13 E F 1 Difference 3.00+.06 2.80±,05 + .20+.08 In no instance are the differences significant, with possibly an exception in the case of flocks E and, F in the pullet year. The fowls well fed while young began to lay at an earlier age than their poorly fed sisters, and as the author has already shown that the younger the bird at the time of laying the first egg the smaller the first few eggs that are laid will be* it would be natural to expect a slight increase in the standard deviation in flocks A, C, and E due to this factor. It is evident from the data submitted in Table X that the manner of feeding the chickens while young had no measurable influence on the standard deviation in the weight of the eggs laid by the mature females. The Standard Deviation in the Weight of Eggs as Influenced by the Season of the Year Do eggs fluctuate more from their mean weight at one sea- son of the year than at another? To answer this question the deviation has been calculated for all six flocks for the laying season of 1922-1923. This was the third year of laying for flocks A and B, the second year for flocks C and D, and the first year for flocks E and F. The results of this computation are shown in Table XL *Bul. 182, p. 7. W. Va. Agr'l Exp't Station, August, 1923. June, l!t2f)) DEVIATION IN WEKiHT OF EGGS IS 4) 'I o : § 2 i u o U] > 0) Q H C « 4^ X QQ < h >— lOOOOOOOOOOrH T-HTfcooococvieocococococo S M't~ -^ 00 O 00 t> lO «0 CO 00 CO t- M t>00^00Ot--^O'*t>rHC<l 5 oacocio'— irHTHcvaoJcoin^o « _o t- c^j 00 M (M oj oi 00 Oi o oj «:> ^oo<xiooa3C~oo^c<i«r>c^ bo c 1 ^ s ' Q TO ti " ^ no e M « y 1. t-OOrHt-t-COC^t-OOrHlO (J'-,>-I,-it-hOOOOOOt-I(M ■^.Sl+l+i+l+i+l+l+i+l+l+i+i > t-^LOLCC<!a3cooo'sfc~C5i toioi-HOiOooooooi-ias' CO 00 ^ co' -^' CO ^ 00 CO 'q^' CO > bo io,-HOOOiocouocoooi-Hco tDio>OT-i«:>oocDiX)'-ioo 5i Oooooio-^cioooic-cooi g rtu^|oco6t-^t>«CTjIooco^'«:><»'2 JJOii^LOiOiOLCLOUOLOlOlCiO'^ b. Id jjjjaii— icDcooo(NiuoOi<M-^oo rj J !OCOT-IOCOCD-^t~OOCOlOo e 2, '-' 1-1 CO t- 00 00 t- t~ LO CO «2- 2W •B s h B -r rt > t/3 Q QQ TJ 4^ bA «• B > bo < bW S«- jt .S u >► b •^rs . * S;j 3 60 2W uocorHiX'^cDcota^ooicoo (MtHi— lOOOoOOO'-l'"' +i +1 +i +1 +i +1 +i +1 +i +i +i +i T-lOLOCO'-IOOrHCOOO(MCO'-l coiHcococococococococo osi-Hcoait-oscoooasco^^ i-ii>ioom(M«Dmt-iooo^ cvicooo-'^'^aic-ocio-^'-^ o<j3ododt>iOTtiOTjicDt>CT3 <fl!COCOCO>-HOiO?DCO'— '00<M C<1 00 00 05 t- 00 t- ^ '-' ojoococococococococococo o: c; c; G5 CTi oj ci CiOi Ci Oi o; >■■ be' ^^ fc § <^ § .? ►^ < w O iz; 14 W. VA. AGR'L EXPERIMENT STATION (Bulletin 195 If the results be disregarded where the number of eggs laid in a month was small, Table XI shows that there was but little difference in the standard deviation during the different months of the year. During May, the month of maximum egg produc- tion, the deviation was slightly smaller than earlier or later, but this difference is too small to bq significant except with flocks E and F. The deviations for flocks C and D average larger than for either flocks A and B or for flocks E and, F. The author is un- able to account for the greater variability in the weight of the eggs laid by these fowls. Correlation Betw^een the Number of Eggs Laid by a Bird and the Standard Deviation in the Weight of the Eggs Is there any connection between the number of eggs that a hen may lay in a season and the extent of their fluctuations in weight? To answer this question the correlations have been calculated and the results are presented in Table XII. TABLE XIL — The Mean Number of Eggs Laid per Bird, the Mean Standard Deviation in the Weight of Eggs, and the Correlation Between the Number of Eggs Laid and the Standard Deviation of Their Weight. First Second Third Flock Year Year Year [' Number of annual records 28 1 23 23 A j Mean number of eg-gs laid 147.00 ±4.47 151.70 ±3.65 138.17 ±3 .40 Mean standard deviation . Coefficient of correlation 3.53 ± .13 2.61 ± .08 2.72 ± .05 + .384± .119 + .035± .140 21 + .052± 21 .140 (' Number of annual records 21 B Mean number of eggs laid 121.29 ±5.15 150.05 ±2.97 129.52 ±3.77 Mean standard deviation .Coefficient of correlation 3.37 ± .13 2.69 ± .07 2.73 ± .07 + .212± .134 — .151± .137 — .155± .137 ( Number of annual records 19 1 19 C j Mean number of eggs laid 140.00 ±4.58 1 146.68 ±3.28 1 Mean standard deviation 3.57 ± .13 1 2.62 ± .05 L Coefficient of correlation + .261± .144! + .087± .054 ' 19 r Number of annual records 19 D Mean number of eggs laid 125.06 ±4.87 142.21 ±4.36 Mean standard deviation 3.41 ± .10 1 2.74 ± .12 I Coefficient of correlation — .117± .1631 + .226± .144 Number of annual records , Mean number of eggs laid 47 E 155.75 ±2.34 Mean standard deviation 3.00 ± .06 1 - Coefficient of correlation .000± .098! Number of annual records Mean number of eggs laid 48 1 p r^7.40 ±3.33 ! Mean standard deviation ~ Coefficient of correlation 2 80 ± .05 1 '^^8± .0971 June, 1925) DEVIATION IN WEIGHT OF EGGS Table XII shows that none of the coefficients of correla- tion are significant with the exception of Flock A for the first year, hence it would appear that there is little or no relation- ship between the number of eggs that a hen may lay and the standard deviation in the weight of the eggs when the standard deviation is based on the production for an entire year. Correlation Betv^reen the Standard Deviation in the Weight of the Eggs Laid byj the Same Fowl from Year to Year If a fowl lays eggs which have a relatively high or low standard deviation in weight, will this relatively high or low standard deviation persist during later years? To answer the question the coefficients of correlation have been calculated and the results are shown in Table XIII. TABLE XIIL — Coefficient of Correlation in the Standard De- viations in the Weight of Eggs During Different Years. ■ Deviation Pullet Year Deviation Second Year Flock Subject; Deviation Subject; Deviation Second Year Relative Third Year Relative A r= + .194±.135 + .360±.122 B r= + .195±.142 1 + .700±.075 C r= + .223±.147 1 D r= + .662+.087 1 All of the coefficients are positive. Two of them are strong- ly significent. The results taken as a whole would seem to in- dicate that the degree of deviation tends to persist from year to year. On the other hand the wide variation in the magnitude of the coefficients indicates that the deviation may be affected by forces other than those which bring about the primary devia- tion. It seems probable that the deviation as measured is the re- sultant of various influences. Some of these may be inherent, others may be the effect of varying environmental conditions which affect not only the number of eggs but also, their weight. Inheritance Is the degree of deviation in egg weight an inheritable char- acteristic? The data available are too scanty to answ^er this question. Breeding experiments should be conducted selecting for high and low variability in egg weight. 16 W. VA. AGR'L EXPERIMENT STATION Abnormal Deviations (Bulletin 195 Table XIV gives the record of bird 509 for her pullet year. During the first six months no unusual^ condition is evident, and the maximum frequency was in the 48.5 gram class. Later in the year the eggs became much heavier, and the maximum fre- quency was in the 64.5 gram class. The record possibly may in- dicate that this bird had two ovaries, one functioning during the first part of the season and the other later. TABLE XIV. — Frequency Chart Showing Distribution of Eggs During the Year, Dec. 1922-Nov. 1923, Laid by Bird 509, Deviation in Weight of Eggs, Mean Weight, and Stand- ard Deviation. Occ^fsaiJ Ja^(/9!3) F£a. rioH. Apr. May JUf^E. Jiji-r A<JO- S^P-r Oct /Vov. l^urtaeR or £6^5 3 0.S 31.5 3i.S 3 3.5 35^ 37.3 ■ 3BJ 40.5 41. S 4i.S 43.S 1 II 1 1 II i 1 Z 3 4S.S ■f-6.S 47.S ■4 a. J Hi II 1 UH III III II / Hfll nil (HI II III II IW nil III III 1 IHII III 1/ III II 1 II III 13 li 20 Z6 ....Li. S0.3 S/.6 62.S S3.S II 1 1 1 III 1 III IHI 1 1 II 1 1 / / 10 z 9 2 5S.S 56.S Sl.S 5B.S .t9 5 1 1 1 1 60.5 6/. 6 61,5 6 3.3 1^4.5 1 1 1 1 1 III 1 1 1 z z 6 5.5 665 6 7.3 63.3 1 1 1 1 1 1 70.3 7/.3 7Z.5 73.5 'iGifT or £ wi 50.4t 5 O/T/trfS. ■,mt6.SI '— 1 1 75.5 76,3 7 7.S 7S.5 1 1 / 1 OF £oot. If n ZO Zl n le IS II J 136 Table No. XV is the record for bird 583 during her pullet year. It is to be observed that the bird laid only 31 eggs, and that the standard deviation in their weight was 7.10 grams or about twice the normal. June. 1925) DEVIATION IN WEIGHT OF EGGS 17 TABLE XV. — Frequency Chart Showing Distribution of Eggs During the Year, Dec. 1922-Nov. 1923, Laid by Bird 583, Deviation in Weight of Eggs, Mean Weight, and Stand- ard Deviation. <*c (I9il) jAn {1913) Fca 1 Apr Mat J'VNM Ji/i.y /lu* 5ipr. Oct. Nay. or £s.3 / 3as 31.3 3Z.S 33 S 3 -4.5 3S.S 36.S 3ZS 38.3 3 9.3 1 1 / / / / 4 0.3 4/..S 42 5 433 44.5 1 1 1 /I 3 4SS 46.S 4Ti 1 1 1 / 1 2 / 48.5 43. 5 1 1 1 1 1 3 SI.5 S2.5 S3.S .?-«.5 1 1 1, 1 III 1 6 2 / 533 563 3 7.3 58.3 1 1 / / 6as 6I.S 6 2.S <53.S 64.3 1 1 / / 6S5 66^S 6 7.3 . 693 70.3 71.5 i 7!.3 \ 73.3 74.5 Ve,6HT Of 9o Devifij 13 6/JHMJ Ei»«7 7.10 GRn^>. 1 7*5 1 76.3 ! 7 7.3 Non„n <F £g«3J 8 a I 3 / 7 3 3/ The Standard Deviation in the Weight of Different Parts of Egga Possibly throwing some light on the causes for fluctuations in Q^gg weight it is interesting to determine whether different parts of an Qgg vary in weight uniformly or whether the fluctu- ations are mainly in some one portion. In bulletin No. 166 of this station the weight of the eggs laid by certain hens and the weight of the yolks of these eggs are reported. The yolks were separated by breaking the eggs into a colander which permitted the major portion of the white to drain away, then carefully transferring the unbroken yolk to a piece of filter paper where it was rolled about, by lifting the edges of the paper, so that the remainder of the white would be absorbed, then transferring to a dish and weighing quickly. 18 W. VA. AGR'L EXPERIMENT STATION (Bulletin 195 The records presented here pertain to the eggs laid by four birds during the months from March to July both inclusive dur- ing 1915 and 1916, the former year being the pullet year for all four fowls. Table XVI shows the mean weight of the eggs, the yolks,, and the white and shell, together with the standard deviations, and the coefficients of variation. Although somewhat foreign to the present study it is im- portant to observe that the increase in the size of the yolks for all four birds from the first to the second year was relatively much greater than the increase in the weight of the remaining portions of the eggs. Stated differently the percentage of the eggs that was yolk was greater the second year than the first. This may be one reason why pullet eggs are' generally found to- be unsuitable for hatching, not only the eggs being small, but the yolks being relatively small for the size of the eggs. Considering now the coefficients of variation it is seen that the variability in the weight of the yolks is slightly greater than the variability in the weight of the eggs or in the weight of the white and shell. It is difficult to understand why this should be, as the development of the yolk is a process extending over several days, while the secretion of the white and the forma- tion of the shell and shell membranes is a very much shorter process, and it would be logical to expect that the result of this shorter process would be the more variable provided that the fluctuations in the weight of the eggs and its parts are due to en- vironmental conditions. This result agrees, however, with that obtained by Jull* who found that "egg weight is the least vari- able; albumen weight slightly more variable than egg weight; yolk weight considerably more variable than albumen weight; and shell weight the most variable." What are the factors that bring about fluctuations in the weight of eggs? The data that has been presented in this pub- lication throws but little light on this general question. Factors Influencing the Weight of Eggs It will be of interest at this place to review briefly the fact- ors that have a pronounced and well authenticated effect upon, the weight of eggs. ♦Poultry Science Vol. III. No. 3 (1924) June. 1!»25) C id w C .5 *> Q no (d (d 0) no C (d J3 be DEVIATION IN WRIGHT OF EGGS +1 +1 + 1 ,-1 -fl -t ^ 19 jG tD d) ^ c vu *J (0 (d C h (d *C > (d Um a S <n iM U 1 o N-< «^ > <1) X U UJ ^ CQ < H 20 W. VA. AGR'L EXPERIMENT STATION (Bulletin 195 In the first place egg size is a breed characteristic ; at one extreme are the Bantams with their small eggs and at the other the Minorcas with their large eggs. The size of the eggs is also an individual characteristic that persists from year to year. In other words in the same breed certain birds habitually lay large eggs and other birds lay small eggs. The age of the fowl has an influence on the weight of the eggs. The mean weight of the eggs laid during the second year of production in this experiment was eleven per cent greater than during the first year, and the increase from the second to the third year was two per cent. Egg weight is intimately associated with body weight. As the pullet becomes heavier the eggs become heavier, and even in the case of the mature females the heaviest eggs are gener- ally laid in winter or early spring when the hens are heaviest. There also seems to be a relationship between the mean weight of a bird and the mean weight of the eggs laid by that bird. Table XVII shows the correlation between the mean weight of the birds and the mean weight of the eggs laid by these birds based on the records of the six flocks. The mean weight of the birds was based on monthly weighings throughout each year for each bird. TABLE XVII. — Correlation Between the Mean Body Weight of the Birds and the Mean Weight of the Eggs Laid by the Same Birds.'" ! Fiock Year Correlation ACE B D F A C B D A B First r = + .418±.059 First '"' r -= + .164±.070 Second | r = + .433+.084 Second | r =- + .528±.077 Third r = + .328±.125 Third r ^ + .553±.102 In every case the coefficient is positive and in most cases, strongly significant, and shows that the heavier birds in these flocks laid, in general, the heavier eggs. // this result should be found to agree with the results ob- tained with other strains and breeds it would enable a breeder to modify quickly the size of the eggs laid by his flock so as to meet his market requirements. *Table XVII is based on 3,636 body weights and 43,809 egg weights. June, 1!»25) DEVIATION IN WEIGHT OF EGGS 21 The weight of the eggs laid by a bird depends to a certain extent upon the rate of production. The author has shown in bulletin No. 182 of this station that the more eggs laid by a flock of fowls during any particular month the smaller are the eggs for that month, and vice versa. On the other hand a bird that is a prolific layer is as apt to lay as heavy eggs as a bird that is a poor layer. This is shown by Table XVIII. TABLE XVIII. — Correlation Between the Number of Eggs Laid by a FoAvI in a Year's Time and the Mean Weight of the Eggs. Flock Correlation ACE I First | r = — .225±.068 B D F I First I r = + .177±.069 A C I Second I r = + .260±.097 B D I Second | r = — .021=t.l07 A I Third | r = + .015±.140 B I Third | r = — .287±:.135 Three of the coefficients are positive and three are nega- tive, and none of them, with the exception of A C E for the first year, are significant. Hence we may conclude that the number of eggs that a hen may lay has no connection with their average size. The characters, number of eggs, and egg size are separate and distinct. The ration has an influence upon the size of the egg. In bulletin 145 of this station the author has shown that a ration that is too scanty in amount, or one which is improperly balanced has a tendency to reduce the size of the eggs. The factors enumerated above as affecting the weight of eggs throw but little light on the reason for the fluctuation in the weight of eggs as it takes place from day to day. In bulle- tin No. 166 of this station it has been shown that if a hen lays for several days in succession and then misses for a day or more, the first egg of the series is generally the heaviest and that there is a fairly regular and gradual decrease in the weight of the eggs toward the end of the series, the last egg being the smallest. This result can be explained by the assumption that the formation of egg substance takes place at a fairly uniform and regular rate during the period when the bird is in produc- tion. Now if the normal or natural weight of the egg laid by a 22 W. VA. AGR'L EXPERIMENT STATION (Bulletin 195 bird is greater than the amount of egg substance that can be elaborated by the bird in twenty-four hours then one or more of three things may happen. First the size or weight of the eggs may become smaller from day to day. There is an abund- ance of data to show that this takes place normally with most fowls. Secondly, the eggs may be laid later and later each day, the bird laying the first egg of the series' say at 9 o'clock in the morning, the second egg at 10 o'clock the next day and. so on, later and later, until a day is skipped entirely. That this is a matter of common occurrence is known to all who trap-nest fowls. Thirdly, the bird may cease laying for a day or more until she catches up with her daily program of production. Based on this conception of the reason for the usual fluctu- ations in egg weight it appears probable that the smaller the decrease in the weight of the eggs laid by a certain bird .from day to day, the better able that bird is to continue tolay without interruption. From this standpoint the standard deviation in the weight of eggs should be negatively correlated with the annual production, when this deviation is based on the weight of the eggs laid during such a short period of time that it is not masked by extraneous influences. If the fluctuations in egg weight from day to day are asso- ciated with the number of eggs or the fecundity of the bird it should be possible to work out a method for predicting the pro- ductive capacity by a study of these fluctuations, and it is the purpose of the author to reexamine the data on which this bul- letin is based with this end in view. A decrease in egg weight from day to day, laying later and later each day, and occasionally missing one or more days when no egg is laid are the results of the inability of the birds to build up enough egg substance in twenty-four hours for the full sized daily egg. From this standpoint anything which will decrease the variability in egg weight should increase the number of eggs which may be laid, and it would appear that further study of the standard deviation in the weight of eggs may be of great value when carried on in connection with investigations in feed- ing and breeding fowls for increased production. HECKMAN BINDERY INC. JUNE 99 |Bo.„a.To.P>.3s^N,KHESTER,